Underground Storage Reservoir Research Articles

Directionality of gravitational and thermal diffusive transport in geologic fluid storage.

Diffusive transport has implications for the long-term status of underground storage of hydrogen (H_{2}) fuel and carbon dioxide (CO_{2}), technologies which are being pursued to mitigate climate change and advance the energy transition. Once injected underground, CO_{2} and H_{2} will exist in multiphase fluid-water-rock systems. The partially soluble injected fluids can flow through the porous rock in a connected plume, become disconnected and trapped as ganglia surrounded by groundwater within the storage rock pore space, and also dissolve and migrate through the aqueous phase once dissolved. Recent analyses have focused on the concentration gradients induced by differing capillary pressure between fluid ganglia which can drive diffusive transport ("Ostwald ripening"). However, studies have neglected or excessively simplified important factors, namely the nonideality of gases under geologic conditions, the opposing equilibrium state of dissolved CO_{2} and H_{2} driven by the partial molar density of dissolved solutes, and entropic and thermodiffusive effects resulting from geothermal gradients. We conduct an analysis from thermodynamic first principles and use this to provide numerical estimates for CO_{2} and H_{2} at conditions relevant to underground storage reservoirs. We show that while diffusive transport in isothermal systems is upwards for both gases, as indicated by previous analysis, entropic contributions to the free energy are so significant as to cause a reversal in the direction of diffusive transport in systems with geothermal gradients. For CO_{2}, even geothermal gradients less than 10^{∘}C/km (far less than typical gradients of 25^{∘}C/km) are sufficient to induce downwards diffusion at depths relevant to storage. Diffusive transport of H_{2} is less affected but still reverses direction under typical gradients, e.g., 30^{∘}C/km, at a depth of 1000m. This reversal occurs independent of the solute's thermophobicity or thermophilicity in aqueous solutions. The entropic contribution also modifies the magnitude of flux where geothermal gradients are present, with the largest diffusive fluxes estimated for CO_{2} with a 30^{∘}C/km gradient, despite the higher diffusion coefficient of H_{2}. We find a maximum flux on the order of 10^{-13} mol/(cm^{2}s) for CO_{2} in the 30^{∘}C/km scenario; significantly lower than literature estimates for maximum convective fluxes in moderate to high permeability formations. Contrary to previous studies, we find that in diffusion and convection will likely work in concert-both driving CO_{2} downwards, and both driving H_{2} upwards-for conditions representative of their respective storage reservoirs.

Quantification of hydrogen depletion and mineral reactivity in underground hydrogen storage reservoirs

The utilisation of renewable energy has surged over the past decades due to shifts in climate patterns and the diminishing reserves of fossil fuels. Among the renewables, hydrogen energy has emerged as a promising clean energy carrier in recent years. In the hydrogen industry, storage faces a notable hurdle due to the relatively low density of hydrogen gas (0.0813 kg/m³ at 25 °C and 1 atm) and its lower storage density (7–27 kg/m³ at 25 °C and 100–400 atm). As a potential remedy, underground hydrogen storage emerges as a viable option, even though it is not without its challenges. Among these challenges, a prominent one involves the diversity in the composition and physical properties of the reservoir due to the influence of both biological and geo-chemical reactions. In this study, an extensive modelling effort was undertaken to gain insights into the impact of both bio and geo-chemical reactions, variations in porosity, hydrogen depletion, and the effects of diffusion across various levels of salinity, pressure, and temperature. Diverse Water/Rock ratios, distinct minerals, and residual gases were also considered. The modelled conditions encompassing mineral properties and parameters led to a cumulative hydrogen loss of 8.38% over a century. From this, 2.31% was identified due to the reactivity in reservoir rock and 6.07% due to the aqueous diffusion to cap rock and its reactivity. Among these reactions, carbonate dissolution emerged as the most noteworthy, resulting in considerable hydrogen loss contingent upon the presence of methanogenesis bacteria. As per the modelled scenario, porosity was reduced in reservoir rock by 0.41%, and in carbonate cap rock, it was increased by 56%, which could increase the hydrogen leakage. Also, methane (CH4) exhibited the most favourable characteristics as a cushion gas due to its lower reactivity. However, it's crucial to acknowledge that these figures could significantly fluctuate based on variations in mineral composition, bacterial populations and their growth, and the prevailing subsurface conditions. These modelled findings can serve as a valuable tool for comprehending the mechanisms of hydrogen loss and mineral reactivity within a given underground system.

Development of experimentally-validated models for nocturnal cooling of thermal systems with photovoltaic thermal (PVT) modules

This present work describes the development of an experimentally-validated (i) detailed mathematical model and (ii) simplified regression model, for the purpose of investigating the thermal performance of photovoltaic thermal (PVT) modules undergoing nocturnal cooling of thermal systems. The detailed mathematical model is useful for hourly, detailed simulation of thermal systems, while the simplified regression model is applicable to situations needing rapid thermal performance assessment and design of PVT systems for cooling. Such models currently do not exist, owing to the difficulty in quantifying relevant thermal radiation parameters. Thus, another outcome of this work is the foundation of a test method for quantifying cooling performance of PVT systems. In developing the detailed hourly model, the mean absolute error between the detailed model and the experiment was found to be 0.74 ± 0.91 K for predicting the fluid outlet temperature. A parametric analysis was conducted to study the effect of some physical and environmental parameters on the PVT performance, and results showed that the nocturnal cooling power increased by up to 45 W/m2 under favorable radiative cooling conditions. The simplified model underpredicts the outlet fluid temperature by up to 2 °C, especially in winter, but serves as a quick, practical design tool, eliminating the necessity of complex input data and heavy computational demands. The simplified PVT performance curve has versatile applications to various thermal energy systems that benefit from integrating PVT nocturnal cooling, such as underground thermal storage reservoirs utilized with ground source heat pumps, buildings, swimming pools, and phase change material applications.

Injectivity Assessment of Radial-Lateral Wells for CO2 Storage in Marine Gas Hydrate Reservoirs

The carbon dioxide (CO2) leak from conventional underground carbon storage reservoirs is an increasing concern. It is highly desirable to inject CO2 into low-temperature reservoirs so that CO2 can be locked inside the reservoir in a solid state as CO2 hydrates. Marine gas hydrate reservoirs and surrounding water aquifers are attractive candidates for this purpose. However, the nature of the low permeability of these marine sediments hinders the injection of CO2 on a commercial scale due to the low injectivity of wells with conventional completions. This study investigates the injection of CO2 into low-permeability marine reservoirs through a new type of well, namely a radial-lateral well (RLW). A mathematical model was developed in this study to predict the CO2 injectivity of the RLW. The model comparison shows that the use of RLW to replace vertical wells can improve CO2 injectivity by over 30 times, and the use of RLW to replace frac-packed wells can increase CO2 injectivity by over 10 times. A case study and sensitivity analysis were performed with field data from the South China Sea. The result of the analysis reveals that the injectivity of the RLW is nearly proportional to reservoir permeability, lateral wellbore length, and the number of laterals. The CO2 injection rate is predicted to be 19 tons/day to 250 tons/day, which is 3 to 15 times higher than the injectivity of frac-packed wells. It is feasible to inject CO2 into the low-permeability, low-temperature marine reservoirs at commercial flow rates. This work provides an analytical tool to predict the CO2 injectivity of RLW in low-temperature marine reservoirs for leak-free CO2 storage.

A Pragmatic Approach to the Economic Assessment of Green Synthetic Methane Power in the Baltics

The synthesis of methane from hydrogen and carbon dioxide creates an energy resource that is suitable for long-term storage. Once this process is powered by renewable electricity, it produces a clean fuel for producing electricity and heat and supports large-scale renewable energy deployment, energy transition and climate change mitigation. This paper proposes a pragmatic approach to assessing the economic potential of synthetic methane-based power. Today, natural gas plays an important role in the Baltic region due to the existing infrastructure, which includes a transmission and distribution pipeline network, gas power plants and a large underground storage reservoir. Replacing natural gas with synthetic methane would fulfil carbon emission reduction ambitions. In this paper, we simulate electricity producers’ actions at market conditions and consider the generation portfolio in the Baltics and the interconnections with Scandinavia and Poland operating in the NORDPOOL electricity market. As a result of these calculations, we obtain the volume of the synthetic gas, the production costs, the volume of gas storage, the installed capacity of the gas power plant, and the investments required to ensure energy transition and system adequacy. These results are essential for the informed decisions made by policymakers, investors and system operators.

Pore-scale mechanisms and hysteresis effect during multi-cycle injection and production process in underground hydrogen storage reservoir

Injection and production of hydrogen gas storage through multiple cycles often lead to significant variations in the gas water occurrence state and the associated relative permeability curve (RPC). In this study, a visual sandstone etching model and numerical simulation method are used to analyze the alteration of the occurrence state after multiple cycles of gas-water inter drive. The influence of the occurrence state on the variation of the RPC is revealed. The experimental results demonstrate that with an increasing number of cyclic injection and production cycles, the gas saturation in the model shows an upward trend, rising from 64.26% to 73.89%. However, the water block phenomenon also increases, leading to only a small amount of gas bubbles undergoing discrete flow, resulting in a reduction of the porosity utilization from 51.06 % to 40.57 %. In different injection and production cycles, the liquid phase at the corners and blind ends of large pores is difficult to displace. The continuity of gas-liquid distribution enhances with the increase in injection and production cycles. The phenomenon of phase trapping during hydrogen multi-cycle injection is evident, and the relative permeability of the gas phase rapidly declines during the imbibition first stage. The difference in gas saturation between the displacement and imbibition processes gradually decreases, reducing from 0.314 to 0.054. The Carlson model achieves a final simulation accuracy of over 90 % for wettability hysteresis. The numerical simulation results indicate that the modified relative permeability curves can more accurately simulate the changes in hydrogen gas storage during injection and production. The relative error of the hydrogen saturation in the uppermost layer of the reservoir at 1673 days of operation is 8.51 %. And the pressure increase is 13.32% without considering the wetting hysteresis model.

Drinking water quality monitoring of centralized water storage reservoirs in various zones of the National University

Physico-chemical and microbiological pollutants may compromise quality of drinking water. This study aims to highlight various physico-chemical and microbial parameters of drinking water samples from centralized water storage reservoirs of National University. Major water quality parameters which were examined in this study includes pH, Electrical conductivity (EC), Turbidity, Total suspended solids (TSS), Total dissolved solids (TDS), Dissolved oxygen (DO), Residual chlorine, Hardness, Alkalinity. Moreover, microbial analysis of water samples was also carried out through Most Probable Number technique (MPN). Results show that all the physico-chemical parameters were within prescribed limits of World Health Organization and Pakistan Drinking Water Quality Standards (WHO/PDWQS) in both underground and overhead water storage reservoirs except DO ( 9.05-9.2 and 9.05-9.1 mg/L ), TSS (10-20 and 3.3-10 mg/L) and residual chlorine (0.08-0.14 and 0.19-0.28 mg/L) respectively. The MPN index values for both underground and overhead water storage reservoirs ranges between 16- >23 and 1.1-12 respectively and it shows high microbial contamination in water due to low detection of residual chlorine. The results highlight that water from centralized water storage reservoirs of National University is unfit for drinking purposes. Statistical analysis such as paired t-test also reveals that water quality parameters from underground and overhead storage reservoirs are not significantly different from each other except EC and TDS having P values <0.05. It is necessary to safeguard water contamination in water storage reservoirs by monitoring regular inspections and chemical cleaning of water storage reservoirs otherwise it will cause serious threats to well-being of the community.
 Key words: water storage reservoirs, drinking water, microbial quality of water, physico-chemical parameters, paired t-test

Tensor-based reconstruction applied to regularized time-lapse data

SUMMARY Repeatedly recording seismic data over a period of months or years is one way to identify trapped oil and gas and to monitor CO2 injection in underground storage reservoirs and saline aquifers. This process of recording data over time and then differencing the images assumes the recording of the data over a particular subsurface region is repeatable. In other words, the hope is that one can recover changes in the Earth when the survey parameters are held fixed between data collection times. Unfortunately, perfect experimental repeatability almost never occurs. Acquisition inconsistencies such as changes in weather (currents, wind) for marine seismic data are inevitable, resulting in source and receiver location differences between surveys at the very least. Thus, data processing aimed at improving repeatability between baseline and monitor surveys is extremely useful. One such processing tool is regularization (or binning) that aligns multiple surveys with different source or receiver configurations onto a common grid. Data binned onto a regular grid can be stored in a high-dimensional data structure called a tensor with, for example, x and y receiver coordinates and time as indices of the tensor. Such a higher-order data structure describing a subsection of the Earth often exhibits redundancies which one can exploit to fill in gaps caused by sampling the surveys onto the common grid. In fact, since data gaps and noise increase the rank of the tensor, seeking to recover the original data by reducing the rank (low-rank tensor-based completion) successfully fills in gaps caused by binning. The tensor nuclear norm (TNN) is defined by the tensor singular value decomposition (tSVD) which generalizes the matrix SVD. In this work we complete missing time-lapse data caused by binning using the alternating direction method of multipliers (or ADMM) to minimize the TNN. For a synthetic experiment with three parabolic events in which the time-lapse difference involves an amplitude increase in one of these events between baseline and monitor data sets, the binning and reconstruction algorithm (TNN-ADMM) correctly recovers this time-lapse change. We also apply this workflow of binning and TNN-ADMM reconstruction to a real marine survey from offshore Western Australia in which the binning onto a regular grid results in significant data gaps. The data after reconstruction varies continuously without the large gaps caused by the binning process.

Innovative Land Arrangement in Combination with Irrigation Methods Improves the Crop and Water Productivity of Rice (Oryza sativa L.) Grown with Okra (Abelmoschus esculentus L.) under Raised and Sunken Bed Systems

The underground water and water storage reservoirs are rapidly depleting due to nominal recharging by the rainfalls making water a scarce resource for irrigation resulting in poor crop growth and production. Irrigation water application should focus on the proficient use of each drop of water. Water productivity (WP) in agriculture can be improved through crop diversification, proper land and water management techniques. Considering this, a field investigation was carried out during 2013–2014 and 2014–2015 to study the crop response of rice (Oryza sativa L.) + okra (Abelmoschus esculentus L.) system to land configurations and irrigation regimes. Three raised-sunken beds (RSB) having width (m) ratios of 1:3, 2:3, 3:3 and two irrigation schedules viz. continuous standing water (CSW) of 5 ± 2 cm depth and alternate wetting and drying (AWD) at 3 ± 1 days interval for rice in sunken bed were tested. Rice yield was more (4.36 and 4.89 Mg ha−1) under CSW irrigation than AWD irrespective of raised bed width. The highest okra yield was noted by 14.09 and 15.43 Mg ha−1 with AWD in 1:3 RSB systems, whereas the lowest yield was recorded in CSW 1:3 RSB systems. Rice equivalent yield (REY) was found as the maximum in AWD than CSW irrespective of raised and sunken bed configurations. The AWD in 3:3 RSB systems exhibited the highest WP of 1.02 and 1.01 kg m−3 during the first and second year of study, respectively. Wider RSB system of land configuration ratio of 3:3 saved about 40–45% of irrigation water. Such information will help in the planning of an innovative intercropping system of summer rice + okra in the field by changing the land configuration to the raised bed and sunken bed with the AWD irrigation system.

Chemical Change Induced by CO <sub>2</sub> Leakage through Wellbore Cement and Casing Interfaces

Damaged wellbores pose some of the greatest risks for CO2 leakage from underground storage reservoirs. If CO2 is injected into the subsurface, leakage may occur through fractures and cracks formed at the cement-casing interface due to deficient well completion, poor mud displacement, or damage during operation or abandonment. A review of the literature has shown that a range of cement fractures can be sealed through calcium carbonate precipitation, given appropriate fluid residence time and initial fracture aperture. In the presence of steel casing, studies have observed that iron carbonate precipitation may also play a key role in fracture sealing. Here we discuss results of cement-steel, cement-cement, and steel-steel core-flood experiments simulating CO2-brine leakage in these systems. The aim of this study is to quantify the chemical changes in the cement and steel materials upon exposure to CO2-equilibrated brine. Using a combination of surface profilometry measurements, X-ray tomography (XRCT) and solution chemistry analyses, we quantified the chemical changes within both the cement and steel phases. These new experimental data are needed to extend chemical degradation models and predict the long-term behavior of the casing-cement interface in the wellbore environment.

An Exploratory Economic Analysis of Underground Pumped-Storage Hydro Power Plants in Abandoned Deep Coal Mines

This study researches the concept of underground pumped-storage hydro power plants in closed-down underground hard coal mines in Germany. After a review on how this could be realized technically, an economic feasibility analysis is presented, with a particular focus on the costs for the underground storage reservoir. The analysis is performed for different lower (i.e., underground) reservoir sizes and temporal arbitrage potentials (peak/off-peak electricity price spreads), and cost uncertainty is dealt with by means of a Monte Carlo simulation for two distinct head heights. The findings regarding costs and acceptability are compared with those of a classic (on-surface) pumped-storage hydro power plant in a mountainous area. Based on a techno-economic evaluation we conclude that under favorable conditions the realization of underground pumped-storage hydro power (UPSHP) plants seems both technically feasible and economically reasonable. More specifically, an extension of a tubular system seems the most promising option. A UPSHP plant in a mineshaft is probably slightly more expensive than a conventional one, an outcome that depends strongly on the feasible head height. However, the significant reduction of the adverse impacts on the landscape and on local residents, as well as a potentially large number of feasible sites in flat terrain, could make UPSHPs an interesting option for the future energy transition, not just in Germany but worldwide at sites where underground mining is being abandoned.

Influence of CO2 on the Electrical Conductivity and Streaming Potential of Carbonate Rocks

AbstractMinimally intrusive geophysical methods are required to monitor CO2 leakages from underground storage reservoirs. We investigate the impact of gaseous CO2 on both electrical conductivity and electrokinetic properties of two limestones during their drainage. These data are contrasted with measurements performed on one clay‐free sandstone. The initial NaCl brine concentrations before drainage (from 8.5 to 17.1 mMol/L) correspond to the limit between freshwater and slightly brackish water. These values are representative to saturated brine formations inside which CO2 can be stored. Using these water salinities, the surface conductivity of the samples represents less than 5% of the overall electrical conductivity. A CO2 release leads to an increase of the electrical conductivity of the rock during drainage in limestones and no change in sandstone. This increase in the electrical conductivity is due to the dissolution of calcite with the concomitant release of Ca2+ and HCO3− in the pore water. It is not due to the CO2 dissociation in the pore water in the pore pressure range 0–0.5 MPa and at a temperature of T = 20 °C. The measurements of the streaming potential show a substantial decrease of the streaming potential coupling coefficient and zeta potential magnitudes after a CO2 release in carbonates. This observation is explained by the increase of the ionic strength of the pore water in the course of the experiment. This change can be used, in turn, to determine calcite dissolution rates from the measurement of the electrokinetic properties.

Reduced Order Modelling for Estimating CO2 Storage and Enhanced Coalbed Methane of Unconventional Coal Seam Reservoirs

Carbon capture, utilization, and storage (CCUS) is a promising technology for mitigating climate change while providing opportunities for the continued use of traditional fuel sources. While difficulties remain for employing carbon capture technologies at a competitive cost, the injection of carbon dioxide (CO2) into underground storage reservoirs is a well-understood process. Still, continuing the development of resource storage estimates for methane (CH4) production and CO2 storage in hydrocarbon reservoirs at a regional scale is an important aspect for incentivizing industrial-scale implementation of CCUS technologies. There are multiple methods for developing CO2 storage and utilization resource estimates with varying degrees of uncertainty. Although static volumetric models can provide quick reservoir estimates, they necessarily include high levels of uncertainty. On the other side of the spectrum, dynamic reservoir simulations can reduce the uncertainty but require significant resources of time and data that may not be available. The Sequestration of CO2 Tool for Enhanced Coalbed Methane (SCO2T-ECBM), a reduced-order model developed in this study, utilizes sensitivity and uncertainty analyses of dynamic reservoir simulations to generate proxy models for estimating both CO2 storage and enhanced coalbed methane (ECBM) resources in unconventional coal seam reservoirs. We compare CO2 storage and utilization resource estimates from SCO2T-ECBM with regional estimates from static, volumetric models. The results indicate that static models may be overly optimistic, particularly in the mid- and high-range estimates. This result is consistent with other studies that have compared static estimates with dynamic simulations, and may suggest a re-evaluation of CO2 storage and utilization resource estimates is needed. SCO2T-ECBM has promise as a useful tool in generating CO2 storage and utilization resource estimates to aid in the deployment of CCUS technology.

Assessment of soil contamination caused by underground fuel leakage from selected gas stations in Riyadh, Saudi Arabia

ABSTRACTSpills and leakage from underground fuel storage tanks (UFSTs) can potentially contaminate soil and groundwater and pose harmful effects to public health and the environment. This study evaluated the feasibility of using volatile organic compounds (VOCs), total petroleum hydrocarbons (TPHs), electrical conductivity (EC), and pH to examine the contamination caused by leaking UFSTs. Screening water assessments for VOCs and general water quality parameters were conducted on the premises of 53 gas stations in Riyadh, Saudi Arabia, to identify potentially contaminated sites, and 25 ground bores were drilled for the quantification of TPH concentrations, EC, and pH values in 407 soil samples. The experimental approach followed in this study included geochemical analyses based on borehole drilling at five targeted gas stations, analyses of water samples from underground storage reservoirs, and analyses of soil core samples obtained from different depths to determine the degree of TPH contamination. Thirty-five VOCs were identified in the water samples collected from gas stations. Methylene chloride, tribromomethane, toluene, chlorobenzene, dibromochloromethane, and benzene were frequently encountered in most of the water samples. Some of these samples exceeded the World Health Organization and Saudi Arabian guidelines for acceptable levels of pH, total dissolved solids, chloride, nitrate, sulfate, calcium, and total hardness. The measured TPH levels were clearly indicative of subsoil contamination and subsequent accumulation in soil over time, particularly at depths of 1–6 m; there was not a noticeable dependence or impact on pH.

ОЦЕНКА УСТОЙЧИВОСТИ ПОДЗЕМНЫХ РЕЗЕРВУАРОВ В МНОГОЛЕТНЕМЕРЗЛЫХ ПОРОДАХ

ОЦЕНКА УСТОЙЧИВОСТИ ПОДЗЕМНЫХ РЕЗЕРВУАРОВ В МНОГОЛЕТНЕМЕРЗЛЫХ ПОРОДАХ

Resurrection at AGL Silver Springs and Wallumbilla: case study of bringing field and surface facilities back to life

AGL acquired the Silver Springs reserves and operations from Mosaic Oil in 2010, including several depleted yet condensate-rich gas fields. Gas was sent from Silver Springs to the Wallumbilla LPG plant (acquired by AGL in 2011) to be refined into sales gas, LPG and condensate. AGL’s objective was to build a commercial underground gas storage facility by converting the Silver Springs gas field into an underground storage reservoir. The business intent was to run the reservoir in alternating injection and withdrawal mode to take advantage of supply and demand economics. Setting up for injection and withdrawal required the commissioning of 10 petroleum producing wells, bi-directional high-pressure flowlines and associated infrastructure. A high-pressure injection compressor was commissioned. Injection of dry sales gas into wells commenced in 2011. Withdrawal at a higher rate than original was facilitated by new separation and dehydration equipment. The Wallumbilla plant was refitted extensively, including flare and venting upgrades and recertification of the pipeline and every pressure vessel on-site. Withdrawal mode operations commenced in October 2015. The LPG plant operability was demonstrated; however, running at design rate was compromised by excessive chilling in the cryogenic section of the Wallumbilla plant, caused by lower than expected LPG quantities in the withdrawn gas. Process engineering work resulted in design of a regenerative heater to warm the sub-cooled gas. The presentation covers the extent of the improvement work and the process investigations, which have formed the basis to ensure future versatile operation.

Development and optimization of an HPLC–DAD method for quantification of six petroleum hydrocarbon compounds in aqueous samples

ABSTRACTBenzene, toluene, and xylene isomers (BTXs) and pyrene, benzo(b)fluoranthene, and benzo(a)pyrene (polycyclic aromatic hydrocarbons) are common pollutants found in many industrial effluents and in aquifers due to fossil fuels spill from underground storage reservoirs. For these reasons, the determination of these compounds has gained importance in the last decades. In this work, a simultaneous, fast, and accurate quantification of six petroleum hydrocarbon compounds (such as BTXs, pyrene, benzo(b)fluoranthene, and benzo(a)pyrene) using a high-performance liquid chromatography–diode array detector method has been demonstrated. The proposed method is suitable for the direct aqueous sample evaluation and also brings advantages, including the use of small volumes of organic solvents, with high resolution, reducing the analysis cost. The method was also checked using synthetic and real samples, including those containing surfactants, commercial gasoline, and river water samples spiked with petroleum hydrocarbon compounds.

What if… We have to rescue the climate?

It's 2076 and the skies are looking decidedly milky. On windy plains and in parts of the seas that have been turned over to wind farms, a different kind of tower has been built alongside the turbines. They suck carbon dioxide out of the atmosphere. Vast parcels of land have been given over to forest. Trees are grown, harvested and burned for energy in power plants that don't let CO2 escape to the atmosphere. Instead, emissions are captured and pumped into underground storage reservoirs. Ships dump powdered minerals into the water to soak up CO, and reduce ocean acidification. Here, Brahic discusses the environmental impact of climate change.

Model validation and stability analysis for operation projects in Jintan Salt Cavern for strategic oil storage of China

Abstract Underground salt cavern oil storage reservoirs have been adopted in many countries because of their long service life, limited space requirements, and low investment cost. In contrast, the use of salt caverns for oil storage is rarely seen in China. Currently there is only one underground salt cavern strategic oil storage reservoir under planning and construction, in the city of Jintan, Jiangsu province. To help understand the thermodynamic behaviors of oil and brine in the salt cavern, a heat and mass transfer model between oil/brine and the cavity wall of the rock salt cavern and a creep contraction model of the salt cavern cavity are established in this paper. These models are based on thermodynamic theory, percolation theory, and creep theory. The combined model is further validated against measurement data collected from rock salt cavern oil storage reservoirs in other countries. With this model, the stability of the oil storage cavern can be explained, and the impacts of typical projects, as described in the Jintan oil storage reservoir development report, can be analyzed. Furthermore, optimal control strategies for the oil storage reservoir under different operating conditions are obtained. The developed model, together with the analytical results, can provide technical guidelines for the construction and operation of a salt cavern strategic oil storage reservoir.

Prevention of Major Accidents of the Aboveground Parts of Natural Gas Storage Technologies and Shale Gas Production Facilities

This article is intended to describe the most significant hazards associated with the operation of the aboveground parts of shale gas production technology and to compare them with possible hazard of the aboveground parts of natural gas storage technologies in underground storage reservoirs (in natural or artificial spaces in underground geological formations). In both cases, in addition to hazards of treatment of methane (natural gas and shale gas), there are used hazardous chemical substances that may threaten employees and surrounding population. These chemical substances are used for extraction or storage of gas. The issue of prevention of serious accidents of aboveground part of technology for the extraction of shale gas has not yet been solved, but the information about safety and environmental aspects of extracting shale gas has already been described in the last two years, in the article (Pointet, 2011). Safety of chemical constituents used as propping agents is described in the study (Waxman at al., 2011). At present there is no specific legislation of European Union regarding the management of risks of shale gas production, but the update of the European directive 96/82/EC includes storage of natural gas in underground storage. The new Directive 2012/18/EU is generally applicable to all such forms of storage, including the storage in natural gas fields (onshore underground gas storage in natural strata, aquifers, salt cavities and disused mines, and chemical and thermal processing operations and storage related to those operations which involve dangerous substances, as well as operational tailings disposal facilities, including tailing ponds or dams containing dangerous substances shall be included within the scope of the Directive). Due to a larger volume of chemical substances stored in the aboveground part of the technology for extracting of shale gas (average amount about 230 m 3 in stage of hydraulic fracturing) compared with volumes of chemical substances used in the aboveground part of technology of underground storage of natural gas (about 50 m 3 ) the technology of shale gas extraction has significantly higher risk. However, in the case that the entire process of storage of chemical substances will be well managed and sufficient measures will be taken to minimize the risk, aboveground part of the technology for extracting of shale gas does not represent a significant difference from warehouses in chemical production plants. From the comparison of hazards of the aboveground parts of natural gas storage technologies in underground storage reservoirs with hazards associated with the operation of the aboveground parts of shale gas production technology is obvious, that future legislation of European Union in the field of major accident prevention should include also the shale gas production facilities. Although a research about hazards of the aboveground part of the shale gas extraction technology has been made to improve the knowledge on this risk source, more research would be required, especially with practical results of detailed risk analysis.